During the last decade it has been an ever lasting demand to offer ecologically justified processing ability as well as to speed up processing of silver halide photographic films, more particularly films coated with high amounts of silver halide. Processing time reduction can, in principle be realized during each of the processing steps as during developing, fixing, rinsing and drying. Said time reduction may however not lay burden on sensitometric properties (shorter developing times, e.g. lowering speed; shorter fixation and/or rinsing times e.g. causing preservation or archivability problems), nor on physical properties of the processed film (e.g. sticking problems of incompletely dried film sheets), etc.. Following measures known from the patent literature can e.g. be taken.
U.S. Pat. No. 5,230,993 describes a photosensitive silver halide material having a polymer capable of providing a cation site in a fixing solution in order to reduce the fixation time in the processing of these materials.
Industrial non-destructive testing materials suitable for rapid processing applications, wherein use has been made from silver halide emulsion crystals rich in silver chloride have e.g. been described in U.S. Pat. No. 5,397,687. In the said US-A hardener-free processing solutions have been used.
Methods of rapid processing, particularly with respect to rapid fixation of films coated with emulsions rich in silver chloride have been disclosed in U.S. Pat. No. 5,298,372, wherein a developer with a high sodium ion content and low developer and fixer replenishing rates are used. In the context of hard copy materials U.S. Pat. No. 5,582,959 and EP-A 0 794 456 are very useful references. In order to realize rapid fixing without sludge formation JP-A 04-42150 describes use of a hardening fixer with a specific molar ratio of sodium to ammonium ion.
It is moreover preferred that processing proceeds without generation of much waste, e.g. with a low level of silver ions in the rinsing water. So in EP-A 0 661 594 a photographic processor with an ion-exchange resin cell for recovering silver from rinse water leaving the rinsing station of the processor, characterized in that it comprises a liquid buffer station between the rinsing station and the resin-cell and flow-control means in order to controll the flowing rate of rinse water from the buffer station to the resin cell. A silver recovery device has further been described in U.S. Pat. No. 5,605,632, wherein the device comprises an ion-exchange resin bed and a pump for directing the solution through the resin bed.
Besides ion-exchange also metal-ion exchange, wherein use is e.g. made from iron wool, is known as an alternative. These methods all have the disadvantage of being cumbersome and, moreover, an additional waste stream is created.
Besides the possibility of desilvering the rinsing water, there is also the possibility to minimize the amount of rinsing water needed. This allows to have the rinsing water treated by specialized companies, since the amounts of water to be treated are smaller.
From an ecological point of view minimization of amounts of rinsing water are thus desirable in order to avoid further waste. The use of cascade fixing also allows to decrease the silver remaining in the rinsing water as has e.g. been described in EP-A 0 598 145 therein a method has been described for processing imagewise exposed photographic silver halide material by conveying said material in succession through at least a developing, a fixing and a rinsing station, wherein said fixing station comprises two distinct tanks, the fixing of the photographic material occurring completely or almost so in the first tank; a replenishment arrangement for replenishing fixer carried-over by the photographic material from the first to the second tank, the silver content of fixer in the first tank is kept below a certain maximum level by electrolytic silver recovery, said photographic material is squeezed at its cross-over from said first to the second tank to limit carry-over of fixer to said second tank; fixer is caused to overflow from said second into said first tank thereby to produce a counterflow of fixer; fixer is caused to overflow from said first tank and is pumped to said second tank, and the silver content in the second tank of said fixing station is kept below 0.05 g of Ag.sup.+ per liter.
A volume of at most 250 ml for the second tank is therefore preferred. Nonetheless, the use of cascade processors usually requires an appreciable investment, and processors which are already in the market become obsolete. (cost brought about by the required expensive adaptions for processors which have a fixing or a rinsing water cascade). There is no desilvering of the fixer fluid wich may also represent an appreciable economical disadvantage.
Electrolysis of processing solutions in order to reduce waste of a heavy precious metal as silver requires the presence of an apparatus providing said electrolysis. Patents related thereto are EP-A 0 598 144, wherein desilvering under potentiostatic conditions has been described in the presence of a reference electrode sensitive to pH differences; U.S. Pat. No. 5,370,781 wherein an easy removal of silver from an electrolytical cell and wherein advantages of less storage and transport space in a flat configuration are claimed; U.S. Pat. No. 5,378,340 wherein an annular contact surface is assured at the upper opening of the electrolytic cell, in order to reduce the risks of a resistive connection to occur; EP-A 0 754 780 wherein the diffusion limitation current density of an electrolytic cell is estimated by measuring a current-flow therethrough and a desilvering current density which is lower than said limitation current density; EP-A 0 803 591 wherein means for switching from potentiostatic to galvanostatic control in response to a cell current above a treshold value when a selected cathode potential is re-established; EP-A 0 844 524, wherein between developing and fixing as an intermediate liquid, used fixer is the treatment liquid in the processing and EP-A 0 851 286, wherein upon starting processing the fixer solution comprises a mixture of fixer starter solution and fixer replenisher solution, wherein said fixer replenisher is the said fixer replenishing solution and wherein said fixer starter solution is the developing solution. As a result the difference between the freshly prepared fixer solution and the fixer solution after seasoning is minimized in order to provide constant sensitometric and physical properties of silver halide photographic materials after rapid processing in solutions, replenished with minimum amounts of said solutions.
Further in order to avoid precipitate of aluminum hydroxide in fixers containing hardening agents as e.g. aluminum salts, it has been established that use of developer solutions comprising ascorbic acid and derivatives, reductones etc., is in favour when no intermediate rinsing step is present between developing and fixing as has been described in EP-Application No. 97203096, filed Oct. 6, 1997.